Field of Invention
The present invention relates to a casing tube and manufacturing method thereof, and particularly to a pre-buried casing tube to fasten the rails with the sleeper during laying the railway transportation system, wherein the casing tube is made of fiberglass reinforced resin composite which is internally dispersed evenly and stable in structure as to enforce strength of the casing tube for satisfying requirements of the casing tube in railway transportation system.
Description of Related Arts
The railway transportation system, especially for a wheeled vehicle running on rails, is an overland transportation to transport passengers or goods. The development of the railway transportation plays an important part in the stability and sustainable development of the modern society.
The railway transportation, represented by new transportation mode such as high-speed rail, subway and express rail line, is a powerful transportation tool and can effectively improve the unbalanced distribution of physical resources and human resources geographically and make the distance of people closer. Therefore, the recent railway transportation system are rapidly improved with worldwide popularity.
The entire railway transportation system, which is a unified whole system, comprises at least a preset railroad and wheeled vehicles running on the railroad. In other words, the railroad is a necessary component of the railway transportation system.
The railroad comprises a plurality of interlinked rails and a plurality of sleepers, wherein the rails are anchored to the sleepers which are provided on the rail-bed at regular intervals, wherein one function of the rail-bed is to support the sleepers and transmit the huge load from the upward of the sleepers to the foundation so as to reduce deformation of the foundation for the sustainability of the railway transportation system. After the rails lay on the sleepers, the major problem is to fasten rails on sleepers stably and reliably. Traditionally, as the sleeper has been molded integrally, a pre-embedded casing tube 10P is placed at the preset position (as shown in FIG. 1) for securely fasten the pre-embedded casing tube 10P in the sleeper. Then by means of screwing, the rail is fastened on the sleeper.
As shown in FIG. 1, the traditional pre-embedded casing tube 10P is made of “nylon 66” integrally. Specifically, the pre-embedded casing tube 10P has a screw channel 11P, wherein the inner surface of pre-embedded casing tube 10P forms a thread portion to define the screw channel 11P for fastening the rail on the sleeper by a screw. The outer surface of pre-embedded casing tube 10P further comprises a preset thread portion. As the sleeper being molded, the pre-embedded casing tube 10P is provided on the preset position, and is molded with the sleeper integrally to fasten the pre-embedded casing tube 10P in the sleeper stably. However, as the sleeper has been molded, the pre-embedded casing tube 10P is fastened to the sleeper linearly. In actual situation, because of sustained mechanical vibrations from the vehicle to the preset rail, it is easy for the pre-embedded casing tube 10P rotated at the clockwise and the counter-clockwise directions along the outer surface of the pre-embedded casing tube 10P and even dropped from the sleeper. These cause serious damages to operation security of the railway transportation system.
Moreover, the pre-embedded casing tube 10P is made of nylon 66. But the strength of nylon 66 is hard to resist the stress generated from sustained mechanical vibrations from the vehicle to the preset railroad for the pre-embedded casing tube 10P. It is relatively easy to shear one set of thread portion in the inner surface of the pre-embedded casing tube 10P by the screw after a period of continuous use. This reason will accelerate the aging of the tradition pre-embedded casing tube 10P. Therefore, the accelerated aging of the pre-embedded casing tube 10P leads to two problems directly. The first problem is the high cost for maintenance of preset railroad. The second problem is the uncertainty of sustainability and security in the railway transportation system.
Otherwise, because of physical properties of nylon 66, there are further three problems of the pre-embedded casing tube 10P.
In relative moist environment, the pre-embedded casing tube 10P will have certain strength after oxidation. However, in actual application, the environment of the pre-embedded casing tube 10P in different locations or environments will have different strengths. In an elevated location, such as Tibet Plateau, the humidity is relatively low that the pre-embedded casing tube 10P is too fragile to resist the stress from sustained mechanical vibrations from the vehicle to the preset railroad. It is easy to damage even using the pre-embedded casing tube 10P in enforced nylon 66. This is the reason of high cost, great difficulty and accelerated damaging of the pre-embedded casing tube 10P in the elevated locations compared to the humid region for laying preset railroads. Also, the corrosion resistance and abrasive resistance of nylon 66 are not good enough which strongly limits application of the pre-embedded casing tube 10P and effects the lifetime of the pre-embedded casing tube 10P negatively.
On the other hand, nylon 66 is easy to be thermal-degraded. As vehicles running on the preset railroad at high speed, the railroad is getting hotter because of the friction of vehicles and railroads. With the increasing temperature of railroad, the environmental temperature of the pre-embedded casing tube 10P will be higher. Under such high environmental temperature for a long period of time, the nylon 66 made pre-embedded casing tube 10P will be thermal-degraded. The thermal degradation mainly shows as cracking of main chain which leads to reduction of molecular weight and melt viscosity. In further degradation, the three-dimensional structure of nylon 66 causes the increase of melt viscosity to be a gel form, and eventually to be insoluble and infusible matter. Therefore, this is a main reason why the durability of the traditional pre-embedded casing tube 10P is low.
Furthermore, as the pre-embedded casing tube 10P is in the humid environment for a long period of time, the insulation ability of the pre-embedded casing tube 10P will be lower and even normal signal transmission will be damaged which is a potential danger to security.